drm/amd/display: Remove redundant FPU guard

The function dcn32_build_wm_range_table call DC_FP_START/END. Drop the
unnecessary FPU guard.

Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Reviewed-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
Signed-off-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>